0.5% starch indicator is usually the substrate of amylase. This kind of substrate is usually made of starch solution, and there is generally no rigid requirement for the specific starch type, but the starch used is generally corn starch or potato starch, because these two starches are easy to obtain and relatively cheap, and their structures are also suitable as substrates for amylase. Under the action of amylase, starch is decomposed into glucose, and in 0.5% starch indicator, the glucose after starch decomposition can react with reactants, thus changing the color of the solution, which is used to judge the degree of enzymatic hydrolysis. Therefore, no matter what kind of starch is used, its main function is as the substrate of amylase.